A Caltech Library Service

Reliability of detrital marine sediments as proxy for continental crust composition: The effects of hydrodynamic sorting on Ti and Zr isotope systematics

Klaver, Martijn and MacLennan, Scott A. and Ibañez-Mejia, Mauricio and Tissot, François L. H. and Vroon, Pieter Z. and Millet, Marc-Alban (2021) Reliability of detrital marine sediments as proxy for continental crust composition: The effects of hydrodynamic sorting on Ti and Zr isotope systematics. Geochimica et Cosmochimica Acta, 310 . pp. 221-239. ISSN 0016-7037. doi:10.1016/j.gca.2021.05.030.

[img] PDF - Accepted Version
See Usage Policy.

[img] PDF (Supplementary data 1) - Supplemental Material
See Usage Policy.

[img] MS Excel (Supplementary data 2) - Supplemental Material
See Usage Policy.


Use this Persistent URL to link to this item:


The isotopic composition of the detrital sediment record harbours a valuable proxy for estimating the composition of the erodible upper crust since the Archaean. Refractory elements such as titanium (Ti) and zirconium (Zr) can display systematic variations in their isotopic composition as a result of magmatic differentiation. Hence, the isotopic composition of such elements in detrital sediments could potentially be used to infer the average composition (e.g., SiO₂ content) of their source region, even when elemental systematics are obfuscated by weathering and diagenetic processes. A key premise of this approach is that the isotopic composition of sediments remains unbiased relative to their protolith. To what extent isotopic fractionation can occur during sedimentary processes, notably the hydrodynamic sorting of heavy mineral assemblages with contrasting isotopic compositions, remains poorly understood. We investigate the effects of such processes on the Ti and Zr isotope composition of a suite of detrital sediments from the Eastern Mediterranean Sea (EMS). These sediments are binary mixtures of two main provenance components, Saharan dust and Nile sediment, with strongly contrasting mineralogical and geochemical signatures. The EMS sediments display clear evidence for hydrodynamic sorting of zircon, expressed as a large variation in Zr/Al₂O₃ and deviation of εHf relative to the terrestrial εNd-εHf array. Our new data, however, do not show pronounced Zr isotope variation resulting from either hydrodynamic sorting of zircon or sediment provenance. Although this agrees with theoretical models that predict negligible equilibrium zircon-melt Zr isotope fractionation, it contrasts with recent observations suggesting that kinetic Zr isotope fractionation might be a common feature in igneous rocks. For the EMS sediments, the negligible shift in Zr isotope composition through hydrodynamic sorting means that fine-grained samples accurately reflect the composition of their source. The nearly overlapping Zr isotope compositions of Sahara- and Nile-derived sediment, however, mean that Zr isotopes, in this case, have insufficient resolution to be a useful provenance proxy. Titanium behaves differently. A small but resolvable, systematic difference in Ti isotope composition is observed between the Sahara and Nile provenance components. Samples with a strong Saharan dust signature show some Ti isotope evidence for hydrodynamic sorting of oxides in tandem with zircon, but a much stronger effect is inferred for Nile sediment. Regression of the EMS sediment samples shows that the Ti isotope composition of the Nile-derived component is strongly fractionated compared to its protolith, the Ethiopian flood basalts. Whereas Ti in Nile sediment is carried in essentially unmodified concentration, and by inference isotope composition, from its sources to the delta, large-scale hydrodynamic sorting of Fe-Ti oxides occurs in the littoral cell. This process causes a decrease in TiO₂/Al₂O₃ of the residual fine-grained sediment fraction and shifts its Ti isotope composition to heavier compositions. The potential of such an “oxide effect” in detrital sediments has implications for crustal evolution models that use Ti isotopes as a proxy for the proportion of felsic crust and can account for the observed scatter in the shale record.

Item Type:Article
Related URLs:
URLURL TypeDescription
Klaver, Martijn0000-0001-5242-7362
Ibañez-Mejia, Mauricio0000-0002-7839-2425
Tissot, François L. H.0000-0001-6622-2907
Additional Information:© 2021 Elsevier Ltd. Received 20 January 2021, Revised 11 May 2021, Accepted 13 May 2021, Available online 21 May 2021. The EMS sediment samples were kindly provided by the DSPD/ODP core repository in Bremen. We thank Liam Hoare for assistance in the lab, Chris Coath for providing the code for some of the regressions and Zhengbin Deng for sharing Nd concentration data for several Afar samples. Careful reviews by Zhengbin Deng and three anonymous reviewers helped improve the paper. Associate editor James Day is thanked for efficient handling of the manuscript. This work was supported by NERC Standard grant NE/R001332/1 and a Royal Society Research Grant to MAM, NSF-EAR grants 2131632 (to MIM) and 1824002 (to FLHT), as well as start-up funds to FLHT provided by Caltech. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
Natural Environment Research Council (NERC)NE/R001332/1
Subject Keywords:Detrital sediments; Hydrodynamic sorting; Ti isotopes; Zr isotopes; Eastern Mediterranean Sea
Record Number:CaltechAUTHORS:20210527-145907147
Persistent URL:
Official Citation:Martijn Klaver, Scott A. MacLennan, Mauricio Ibañez-Mejia, François L.H. Tissot, Pieter Z. Vroon, Marc-Alban Millet, Reliability of detrital marine sediments as proxy for continental crust composition: The effects of hydrodynamic sorting on Ti and Zr isotope systematics, Geochimica et Cosmochimica Acta, Volume 310, 2021, Pages 221-239, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109284
Deposited By: Tony Diaz
Deposited On:27 May 2021 22:30
Last Modified:13 Sep 2021 20:25

Repository Staff Only: item control page